
A recent study is highlighting worries about an uncommon yet serious risk associated with a prevalent sexual practice — the possibility of brain injury and dementia triggered by the herpes simplex virus type 1 (HSV-1).
HSV-1, the virus that leads to oral herpes, is carried by nearly four billion individuals worldwide. While it primarily causes cold sores, researchers have recently uncovered a concerning pathway through which the virus can access the brain — through the nasal route during oral sexual activity.
Professor Deepak Shukla from the University of Illinois Chicago, who spearheaded the study, indicated that HSV-1 particles can enter the nasal cavity if it comes into contact with the saliva or skin of an infected partner during oral sex. Once inside the nose, the virus can travel directly to the brain, raising the risk of encephalitis, brain damage, and potentially dementia.
The study, published in the journal *mBio*, also pinpointed a critical human enzyme, **heparanase (HPSE)**, that might make nasal HSV-1 infections particularly dangerous. Although heparanase generally helps to clear damaged cells, HSV-1 seems to exploit this enzyme to amplify inflammation in the brain.
“For the majority, HSV-1 results in occasional cold sores and is not harmful,” stated Professor Shukla. “However, if the infection ascends through the nasal route to the brain, it can be far more severe.”
To investigate this hypothesis, Shukla’s team performed experiments on mice by introducing HSV-1 into their nasal passages. Mice with normal heparanase levels developed serious symptoms such as nasal swelling, respiratory issues, and ultimately death. Brain analyses revealed nerve damage, significant inflammation, and unusual activity in regions associated with olfaction and viral entry.
Behavioral changes were also observed, including memory impairment, anxiety-like behaviors, and coordination difficulties — all within six months of infection.
Though herpes simplex encephalitis (HSE) is uncommon — impacting roughly two to four individuals per million — researchers suspect that cases of nasal HSV-1 are likely underreported. The virus may remain latent in the brain and contribute to conditions like Alzheimer’s disease in later life.
Shukla stressed that the impact can vary widely based on a person’s immune health and the frequency of outbreaks.
“Our research acts as a cautionary tale,” he remarked. “Uncontrolled herpes can lead to long-lasting behavioral problems, motor dysfunction, and issues with coordination. It’s crucial to comprehend how the virus operates and the severity it can reach under specific circumstances.”
Professor Deepak Shukla from the University of Illinois Chicago, who spearheaded the study, indicated that HSV-1 particles can enter the nasal cavity if it comes into contact with the saliva or skin of an infected partner during oral sex. Once inside the nose, the virus can travel directly to the brain, raising the risk of encephalitis, brain damage, and potentially dementia.
The study, published in the journal *mBio*, also pinpointed a critical human enzyme, **heparanase (HPSE)**, that might make nasal HSV-1 infections particularly dangerous. Although heparanase generally helps to clear damaged cells, HSV-1 seems to exploit this enzyme to amplify inflammation in the brain.
“For the majority, HSV-1 results in occasional cold sores and is not harmful,” stated Professor Shukla. “However, if the infection ascends through the nasal route to the brain, it can be far more severe.”
To investigate this hypothesis, Shukla’s team performed experiments on mice by introducing HSV-1 into their nasal passages. Mice with normal heparanase levels developed serious symptoms such as nasal swelling, respiratory issues, and ultimately death. Brain analyses revealed nerve damage, significant inflammation, and unusual activity in regions associated with olfaction and viral entry.
Behavioral changes were also observed, including memory impairment, anxiety-like behaviors, and coordination difficulties — all within six months of infection.
Though herpes simplex encephalitis (HSE) is uncommon — impacting roughly two to four individuals per million — researchers suspect that cases of nasal HSV-1 are likely underreported. The virus may remain latent in the brain and contribute to conditions like Alzheimer’s disease in later life.
Shukla stressed that the impact can vary widely based on a person’s immune health and the frequency of outbreaks.
“Our research acts as a cautionary tale,” he remarked. “Uncontrolled herpes can lead to long-lasting behavioral problems, motor dysfunction, and issues with coordination. It’s crucial to comprehend how the virus operates and the severity it can reach under specific circumstances.”